If you want to handle IPV6 in standard notation there are 8 groups of 4 hex digits:
2001:0dc5:72a3:0000:0000:802e:3370:73E4
32 hex digits + 7 separators = 39 characters.
CAUTION: If you also want to hold IPV4 addresses mapped as IPV6 addresses, use 45 characters as @Deepak suggests.
